This invention relates to a magnetron capable of preventing loss and leakage of microwave energy through an electroconductive sealing member interposed between the output member of the magnetron and the anode cylinder.
As shown in FIG. 1, in a prior art magnetron, an output member 3 is coupled to an anode cylinder 1 containing an oscillator cavity of a well known construction through a sealing member 2, and a cap 4 is mounted on the output member 3 to constitute an antenna.
Since the purpose of the gasket member 13 is to prevent leaks of microwave, it is made of electroconductive material, such as a fine wire net. An insulator 6 is sealed to the opposite end of the anode cylinder 1 via cup shaped sealing members to form a stem. A plurality of radially extending heat dissipating fins 7 are secured to the periphery of the anode cylinder 1. A pair of annular permanent magnets 8 and 9 are disposed to surround cup shaped sealing members 2 and 5 respectively. The permanent magnets 8 and 9 are supported by magnetic casings or yokes 10 and 11 which form a magnetic circuit for the magnetic flux produced by the permanent magnets 8 and 9. An annular gasket support 12 is disposed between the permanent magnet 8 and the yoke 10 to support a gasket member 13 disposed between the cup shaped sealing member 2 and the permanent magnet 8. A high frequency device such as a waveguide is urged against the gasket member 13 by screws or the like to bring the cup shaped sealing member 2, yoke 10 and the gasket support 12 into good electric contact with the gasket 13 to propagate the microwave energy through the coupling between the magnetron and the high frequency joint without loss and leakage.
Since in the prior art magnetron described above, the gasket support 12 is an indispensable element, the cost of manufacturing the magnetron increases. Moreover, since the gasket member 13 must have a sufficiently large resiliency, it is desirable to make large its thickness. Although the yoke 10 may have a thickness sufficient to provide a low reluctance flux passage, if its thickness is made to be smaller than that of the gasket member 13 there is a fear of dropping off of the gasket member 13 during transportation of the magnetron. For this reason, the thickness of the yoke 10 must be larger than that of the gasket member 13, thus increasing the weight and cost of manufacturing. Moreover, since the gasket member 13 is fitted between the yoke 10 and the cup shaped sealing member 2, it is necessary to assemble the yoke 10 with a perfect concentric relation with respect to the cup shaped sealing member 2. To this end it is necessary to use a special jig which degrades workability.